Glassworking methods



Patented May 20, 1952 UNiT-E o srAr ss ration of New York No Drawing. Applicationfibveniliefta194d, Serial No. 129,195

5 Claims. (of. 49-85 The present invention relates to improvements in glass article-pressing methods.

In the automatic pressing of glassware there is frequently experienced, as the use ofamold is lico ntinued, a gradual development of a haze pat- "tern-over a greater or smaller portion of the surface of the article being produced. The formation of this haze pattern is generally encountered with certain types of glasses, especially those which contain constituents that are more or less volatile at the pressing temperatures. Examination of molds producing such haze patterns .indicates that a deposit has been built up on the mold surface, so far as can be determined, by the condensation and accumulation thereon of constituents that have been volatilized or stewed out of the charges of molten glass as they have been successively pressed in the molds. Apparently, even though the plunger in pressing each charge may tend to shift these constituents from their initial area of deposition, it nevertheless, because the successive charges are all deposited in the mold in the same position, always shifts them in the same directions and to the same location. The result is that, after a limited period of operation, a sufficient quantity of such volatilized constituents accumulates to result in the creation of a loading mark in the mold and the accompanying haze pattern on the pressed ware surfaced.

Although the development of such a haze pattern is not particularly objectionable in many articles so long as it remains relatively unnoticeable to the casual observer, it becomes of primary importance in those articles such as television picture-tube panels and the like where a high degree of surface quality is renuired. In such cases it has been the usual practice heretofore to replace each mold after it has been in use for only a relatively short time and before any significant deposit has been formed thereon, with a resulting increase in downtime and operating cost. It has been proposed to alleviate this condition by making provision for periodically brushing or otherwise cleaning the molds as they are being used, but such practice has not been found particularly helpful or feasible.

The primary object of the present invention is the provision of an improved method of glassworking which is free of the faults above described.

It has now been discovered that the formation of the deposit on the mold surface can be materially reduced and even substantially avoided, with a consequent minimization or elimination ha'z pattern in thfe pifes'sed ware, by feeding the-'succes's'ive-charges of molten glass in such away that each succeeding charge or group of charges is positioned on a surface portion of the mold different from that on which the preceding charge-or group of charges was deo'r tlr -prbeu uon or a.

osited. Any constituents which volatilize or stew out of the Successive glass charges and acmark can be substantially mitigated where the deposited constituents are distributed relatively uniformly over the entire mold surface.

A further advantage of the present invention is that uneven heating of the mold as a result of the repeated deposition of glass charges on the identical mold surface area is avoided, and the life of the mold thereby is considerably lengthened. Moreover, the breakage of ware prior to annealing, because of strains set up therein by reason of a non-uniform'mold temperature, can thus be reduced to a minimum.

A simple way to carry out applicants method when, for example, pressing television picturetube panels on an indexing-type rotating table press is to mount the molds for rotary movement about their own axes and to then give each mold a turning movement through a 15 to 30 arc following each use. Alternatively, the trough used to direct the charges into the mold can from time to time be slightly shifted relative to the mold to successively deposit the respective charges on different mold surface portions. In either event, the operation can be carried out manually, or suitable provision can be made to effect the same automatically.

The invention is of course more readily applicable to the manufacture of articles that are circular in cross-section or that are formed with plungers which are circular in cross-section; but it is not necessarily limited to the manufacture of such articles. If the articles to be pressed require a rotary position of orientation with respect to the plunger, as is the case with a square or a rectangular-shaped article, the method can be carried out by shifting of the feeder trough, as above described, or, alternatively, by from time to time imparting uniform turning movements to both the mold and, it necessary, the plunger about their common axes.

When one of the foregoing improved methods is followed, the need for cleaning the mold is substantially obviated, the mold life is prolonged, and more and better ware is produced.

What is claimed is:

1. The method of forming glass articles, which includes successively feeding a mold with a series of charges of molten glass, depositing at least one charge of the series on one surface portion of the mold and forming such charge into an article, and depositing a subsequent charge of the series on another surface portion of the mold difierent at least in part from said one surface portion and forming the latter charge into a similar article.

2. The method of forming glass articles, which includes successively feeding a mold with a series of charges of molten glass by depositing each charge of the series on a surface portion of the mold diiferent at least in part from that on which the preceding charge was deposited, and forming an article in the mold, following the deposit of each charge therein.

3. A method such as defined by claim 2, wherein the charges are all fed from the same point of 4 delivery and the mold is shifted with respect to such point for each successively fed charge.

4. A method such as defined by claim 2", wherein the mold is stationary and the point of delivery of the charges is shifted.

5. The method of forming a plurality of glass articles successively in a press mold, which includes depositing a charge of molten glass onto one surface area of the mold, pressing such charge into the desired article, removing the article from the mold, depositing another charge of molten glass onto a surface area of the mold at least in part differing from the surface area onto which the preceding charge was deposited, and pressing the last-deposited charge into the desired article.

CHARLES W.DOYI.LE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,015,219 Gray et a1. Sept. 24, 1935 2,162,800 Crimmel June 20, 1939 

